Regarding a switchgear such as a gas-insulated switchgear having an electric current shut-off part, there exists, for example, as a driving device for driving a moving contact constituting the electric current shut-off part, a hydraulic operation device which is equipped with a pressure accumulator using a compressed gas such as N2 gas and which causes a pressure oil due to this pressure accumulator to act on a piston to perform the opening/closing operation, or a spring operation device which exerts the repulsive force of an energy storing coil spring or a disk spring to perform the opening/closing operation.
Of these, in the hydraulic operation device, a compressed gas such as N2 gas is used in the pressure accumulator serving as the drive source, so that the gas undergoes expansion/contraction due to a change in the ambient temperature, and, in some cases, the hydraulic oil pressure undergoes fluctuation. On the other hand, the spring operation device requires a complicated mechanism, which involves a large number of components, making it necessary, in some cases, to conduct maintenance (See Patent Document 1).
Meanwhile, there is known a hydraulic operation device which utilizes no compressed gas and in which there is provided a mechanism effecting pressure accumulation by a turning-off pressure accumulation spring and a turning-on pressure accumulation spring such that the hydraulic oil pressure does not undergo fluctuation due to a change in the ambient temperature, thus reducing the complicated mechanism part (See Patent Document 2).
Further, Patent Document 3 discloses a device which is not a hydraulic operation device but a spring type operation device and in which an opening spring is arranged on the radial side of a closing spring.